1. Field of the Invention
This invention relates to a swivel type fluid coupling for use with boom supported hydraulic tools, and in particular to the provision of a low resistance fluid coupling which is relatively small and compact, and to a manner of protecting such coupling against contact damage.
2. Description of the Prior Art
It is common to mount hydraulic tools, such as hydraulic rock breakers, compactors, etc., on the end of a boom carried by a construction vehicle. The tool is mounted for pivotal movement relative to the boom and the boom is itself pivotally mounted on the vehicle. The boom is swung up and down and sideways for positioning the tool. The tool itself is swung relative to the boom for attitude control. Hoses are used for delivering hydraulic fluid from the vehicle to the tool and from the tool back to the vehicle. The tool ends of the hoses are pivotally attached to the tool and the hoses hang free to a degree as they extend back to the vehicle. Presently, it is common to provide an elbow type swivel coupling on each side of the tool. The supply hose is connected to one such coupling and the return hose is connected to the other. It is also common practice to provide the hydraulic tool with shield plates for the couplings, positioned between the couplings and whatever material might be located immediately forwardly of the tool in the vicinity of the couplings.
A disadvantage of side located swivel couplings is that they are not adequately protected against damage from encounters with materials which during use of the tool may be located immediately sideways of the coupling. Also, the known forms of elbow type swivel couplings are relatively large and this contributes to the problem of being able to adequately protect them from damage.
It is an object of the present invention to provide a single swivel coupling for connecting both the hydraulic supply and return hoses to the hydraulic too. The concept of a single swivel coupling for handling both supply and return flow is broadly known in other environments, examples of which are disclosed by the following U.S. Pat. Nos.: 2,710,598, granted June 14, 1955, to Erwin Baas; 2,790,426, granted Apr. 30, 1957 to Otto Mueller; 3,446,305, granted May 27, 1969 to Craig W. Cannon and 3,678,810, granted July 25, 1972 to Lloyd H. Holmes and William D. Dundland.
The type of coupling disclosed by U.S. Pat. Nos. 2,710,598; 2,790,426 and 3,446,305 is basically characterized by a sleeve which is mounted for pivotal movement about a tubular shaft. An annular chamber is formed in the sleeve about the shaft. A plurality of radial ports are formed in the shaft for communicating the interior of the shaft with the annular chamber. A disadvantage of this type of swivel is that because of the radial port arrangement high energy losses are experienced unless the hardware is made quite large.
The coupling disclosed by U.S. Pat. No. 3,678,810 is a very complex specialized form of coupling which would not be suitable for connecting supply and return hoses to a hydraulic tool because it involves concentric passageways.